Since the Environmental Movement began, adolescents' views have been largely ignored in studies of public opinion. The article presents a descriptive analysis of trends in the environmental attitudes, beliefs, and behaviors of high school seniors from 1976 to 2005 using data from the Monitoring the Future study. Across a range of indicators, environmental concerns of adolescents show increases during the early 1990s and declines across the remainder of the three decades. Declining trends in reports of personal responsibility for the environment, conservation behaviors, and the belief that resources are scarce are particularly noteworthy. Across all years, findings reveal that youth tended to assign responsibility for the environment to the government and consumers rather than accepting personal responsibility. Recent declines in environmental concerns for this nationally representative sample of youth signal the need for a renewed focus on young people's views and call for better environmental education and governmental leadership. (Contains 2 tables, 5 figures, and 2 notes.)